The Experts below are selected from a list of 1632 Experts worldwide ranked by ideXlab platform
Chun-jiang Wang - One of the best experts on this subject based on the ideXlab platform.
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catalytic asymmetric synthesis of quaternary trifluoromethyl α to e amino acid derivatives via Umpolung allylation 2 aza cope rearrangement
Chemical Science, 2020Co-Authors: Xishang Sun, Liang Wei, Hai-yan Tao, Chun-jiang Wang, Xingheng WangAbstract:In this study, we developed an efficient Ir-catalyzed cascade Umpolung allylation/2-aza-Cope rearrangement of tertiary α-trifluoromethyl α-amino acid derivatives for the preparation of a variety of quaternary α-trifluoromethyl α-amino acids in high yields with excellent enantioselectivities. The Umpolung reactivity empowered by the activation of the key isatin-ketoimine moiety obviates the intractable enantioselectivity control in Pd-catalyzed asymmetric linear α-allylation. In combination with quasi parallel kinetic resolution or kinetic resolution, the generality of this method is further demonstrated by the first preparation of enantioenriched quaternary trifluoromethyl β-, γ-, δ- and e-amino acid derivatives.
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catalytic asymmetric synthesis of α trifluoromethyl homoallylic amines via Umpolung allylation 2 aza cope rearrangement stereoselectivity and mechanistic insight
Organic Letters, 2019Co-Authors: Limin Shi, Hai-yan Tao, Chun-jiang Wang, Xishang Sun, Chong Shen, Zuofei WangAbstract:An unprecedented Ir-catalyzed asymmetric cascade Umpolung allylation/2-aza-Cope rearrangement of trifluoroethylisatin ketimines has been realized. The current method provides a facile access to biologically important α-trifluoromethyl-containing homoallylic amines in high yields with excellent enantioselectivity. Notably, Umpolung reactivity of trifluoroethylisatin ketimine was discovered for the first time. Mechanism studies revealed the key intermediates in the initial Umpolung allylation and the stereospecific chirality transfer in the subsequent 2-aza-Cope rearrangement.
Min Shi - One of the best experts on this subject based on the ideXlab platform.
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pd ii catalyzed and diethylzinc mediated asymmetric Umpolung allylation of aldehydes in the presence of chiral phosphine schiff base type ligands
ChemInform, 2011Co-Authors: Jiajun Jiang, De Wang, Wenfeng Wang, Zhiliang Yuan, Meixin Zhao, Fei Jun Wang, Min ShiAbstract:Asymmetric Umpolung allylation of aromatic aldehydes (II) proceeds smoothly in the presence of a novel Pd—chiral phosphine-Schiff base catalyst to give the homoallylic alcohols (III) in excellent syn-diastereoselectivity and up to 67% optical purity.
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pd ii catalyzed and diethylzinc mediated asymmetric Umpolung allylation of aldehydes in the presence of chiral phosphine schiff base type ligands
Tetrahedron-asymmetry, 2010Co-Authors: Jiajun Jiang, De Wang, Wenfeng Wang, Zhiliang Yuan, Meixin Zhao, Fei Jun Wang, Min ShiAbstract:Abstract Chiral phosphine-Schiff base type ligand L3 prepared from ( R )-(−)-2-(diphenylphosphino)-1,1′-binaphthyl-2′-amine was found to be a fairly effective chiral ligand for the Pd(II)-catalyzed and diethylzinc-mediated enantioselective Umpolung allylation of aldehydes to give homoallylic alcohols in good yields, moderate enantioselectivities and high syn diastereoselectivities.
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chiral bis nhc palladium ii complex catalyzed and diethylzinc mediated enantioselective Umpolung allylation of aldehydes
ChemInform, 2009Co-Authors: Wenfeng Wang, Tao Zhang, Min ShiAbstract:A series of chiral bis(NHC)−Pd(II) complexes bearing different coordinating counterions have been prepared and successfully applied in Et2Zn-mediated enantioselective Umpolung allylation of aldehydes with cyclohexenyl acetate, affording the homoallylic alcohols in moderate to excellent yields (up to 96%), modest enantioselectivities (54%−66% ee), and good to excellent syn diastereoselectivities (up to 99:1 dr).
Ohyun Kwon - One of the best experts on this subject based on the ideXlab platform.
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stereoselective syntheses of α β unsaturated γ amino esters through phosphine catalyzed γ Umpolung additions of sulfonamides to γ substituted allenoates
Tetrahedron Letters, 2015Co-Authors: Qingfa Zhou, Kui Zhang, Ohyun KwonAbstract:α,β-Unsaturated γ-amino esters can be synthesized efficiently and stereoselectively through phosphine-catalyzed γ-Umpolung additions of sulfonamides to γ-substituted allenoates. The structures of the sulfonamide and γ-substituted allenoate partners can be varied to achieve a range of α,β-unsaturated γ-amino esters with potentially interesting chemical and biological properties.
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chiral phosphines in nucleophilic organocatalysis
Beilstein Journal of Organic Chemistry, 2014Co-Authors: Yumei Xiao, Zhanhu Sun, Hongchao Guo, Ohyun KwonAbstract:This review discusses the tertiary phosphines possessing various chiral skeletons that have been used in asymmetric nucleophilic organocatalytic reactions, including annulations of allenes, alkynes, and Morita–Baylis–Hillman (MBH) acetates, carbonates, and ketenes with activated alkenes and imines, allylic substitutions of MBH acetates and carbonates, Michael additions, γ-Umpolung additions, and acylations of alcohols.
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phosphine catalyzed intramolecular γ Umpolung addition of α aminoalkylallenic esters facile synthesis of 3 carbethoxy 2 alkyl 3 pyrrolines
Chemical Communications, 2012Co-Authors: Ian P Andrews, Brian R Blank, Ohyun KwonAbstract:An array of N-tosylated α-aminoalkylallenic esters was prepared and their cyclization under the influence of nucleophilic phosphine catalysts was explored. The α-aminoalkylallenic esters were prepared through aza-Baylis–Hillman reactions or novel DABCO-mediated decarboxylative rearrangements of allenylic carbamates. Conversion of these substrates to 3-carbethoxy-2-alkyl-3-pyrrolines was facilitated through Ph3P-catalyzed intramolecular γ-Umpolung addition.
Takayuki Doi - One of the best experts on this subject based on the ideXlab platform.
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asymmetric palladium catalyzed Umpolung cyclization of allylic acetate aldehyde using formate as a reductant
ChemInform, 2015Co-Authors: Hirokazu Tsukamoto, Ayumu Kawase, Takayuki DoiAbstract:The first example of an enantioselective Umpolung cyclization of allylic acetates or aldehydes is described.
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asymmetric palladium catalyzed Umpolung cyclization of allylic acetate aldehyde using formate as a reductant
Chemical Communications, 2015Co-Authors: Hirokazu Tsukamoto, Ayumu Kawase, Takayuki DoiAbstract:Palladium/chiral diphosphine-catalyzed Umpolung cyclization of allylic acetate-aldehyde using formate as a terminal reductant affords cis-disubstituted pyrrolidine, tetrahydrofuran, and spiro carbocycle in high enantioselectivity. The formate does not cause allylpalladium reduction under the catalysis. The highly stereoselective cyclization would proceed through a cationic η1-allylpalladium ligated by diphosphine.
Xia Zhang - One of the best experts on this subject based on the ideXlab platform.
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Intramolecular Umpolung Allylation of Imines
Organic Letters, 2018Co-Authors: Miao Zhan, Xiang Pu, Bin He, Xia ZhangAbstract:An intramolecular Umpolung allylation of imines is reported. This reaction occurs via the intermediacy of 2-azaallyl anions. It could proceed either under transition-metal-catalyzed conditions or under transition-metal-free conditions. Importantly, this approach afforded trans-3-vinyl-4-aminochromanes with high diastereoselectivity, while conventional, nonUmpolung methods often display high cis-selectivity.
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Catalytic Asymmetric Umpolung Allylation of Imines.
Journal of the American Chemical Society, 2016Co-Authors: Xia ZhangAbstract:Here we report an iridium-catalyzed asymmetric Umpolung allylation of imines as a general approach to prepare 1,4-disubstituted homoallylic amines, a fundamental class of compounds that are hitherto not straightforward to obtain. This transformation proceeds by a cascade involving an intermolecular regioselective allylation of 2-azaallyl anions and a following 2-aza-Cope rearrangement, utilizes easily available reagents and catalysts, tolerates a substantial scope of substrates, and readily leads to various enantioenriched, 1,4-disubstituted homoallylic primary amines.